Expression control



June 14, 1955 J KQEHL 2,710,556

EXPRESSION CONTROL Filed Feb. 13, 1953 United States Patent Ofiice2,710,556 Patented June 14, 1955 EXPRESSION CONTROL James A. Koehl,Evanston, Ill., assignor to Central C0mmercial Industries, Inc., CookCounty, 111., a corporation of Delaware Application February 13, 1953,Serial No. 336,781

2 Claims. (Cl. 84-1.09)

This invention relates to expression controls and more particularly to atype of control for use in the tone signal translating circuit of anelectrical keyboard musical instrument employing means for producingaudio frequency tone signals which may be selectively translated intoaudible tones for musical expression upon playing the instrumentskeyboard. An instrument of this class is disclosed in my prior PatentNo. 2,250,065, in which patent, a loudspeaker is connected to the outputcircuit of an audio amplifier whose input circuit is provided with apotentiometer or other equivalent well-known impedance regulating devicefor controlling the magnitude of sound emitted at said loudspeaker.

Volume control devices of the type and for the purpose above stated maybe manually operated in any well known manner such as by the foot or theknee of the w player. Keyboard musical instruments employing ahorizontally movable lever for controlling the volume of sound isdisclosed in the Hammond Patent No. 2,203,569.

The invention disclosed in my aforestated patent is a combined piano andelectric organ employing means enabling the playing of piano and organmusic either separately or together and in various combinations for manyversatile musical effects.

It suffices here to say that the herein disclosed invention is anattachment for use particularly with a kneeoperated volume or expressioncontrol device, whereby said device can be operated either by the kneeor the foot of the player as may be found satisfactory for desiredrendition of different musical scores. When such a device is used with apiano which requires frequent operation of the pedals of the piano,there are times when it is both convenient to operate the pedals by thefoot and simultaneously operate the volume control device by the knee.Musical instruments of the class stated are also frequently providedwith a pedal keyboard for sustained bass notes,

the same situated generally to the left of the pedals of the piano asshown in the patent to French No. 2,625,070.

An object of the instant invention is the provision of a footpedal-motion-transferring mechanism adapted to be connected to thecontrol shaft of a knee-operated expression control device to enable thedevice to be operated as desired either by the knee or by the foot ofthe player for satisfactory musical expression.

Nothing herein shall be considered as a limitation upon the type ofelectrical volume control device used in carrying the invention intopractice. The device may be of the constructional order of themechanisms shown in patents, Nos. 1,746,411, 1,920,217, and 2,135,309,or the electrical equivalents of said mechanisms, provided only that themovable controlling element of the mechanism shall have a shaft which isvertically disposed and is free for rotational movement from an offcondition when the shaft is turned a given degree in one direction to anon condition with variations in the volume of sound when the shaft isturned in an opposite direction.

A further important object of the invention resides in the simplicity ofthe constructional elements employed Lil and their form and generaldesign enabling attachment of the device to a knee-operated expressioncontrol.

A still further object of the invention is the provision of afoot-operated pedal mechanism which may be rigidly connected with thecase of a piano so that the motion transferring means of the inventionmay be properly aligned with a coacting part of a knee-operatedexpression control.

The invention consists further in the matters hereinafter described andclaimed.

In the accompanying drawings:

Figure l is a phantom perspective view of a portion of a keyboardmusical instrument showing my invention applied to the instrumentsknee-operated expression control device;

Figure 2 is a sectional perspective view of the invention showing samedisassembled from the control shaft of the knee-operated expressioncontrol;

Figure 3 is a perspective view of the shaft coupling; and

Figure 4 is a view partly in elevation and partly in section showing theinvention in its operative relationship to the control shaft of theinstruments knee-control device.

In Figure 1 is shown a keyboard musical instrument 10 which may be inform of an upright piano having the customary keyboard 11 supported bybed plank 12 and provided with a vertical kneeboard 13 which forms acontinuous part of the case of the instrument. Medially of the oppositeends of the piano are the customary footoperated pedals 14. Supported bythe bed plank 12 is a panel structure 14 which constitutes an element inan organization of elements for the electrical generation of sustainedmusical tones as provided for in my Patent No. 2,250,065. in said patentthe input circuit to an audio amplifier is provided with a variableimpedance for controlling the volume of sound emitted at the loudspeakerwhich forms part of an electroacoustical signal translating system. Aspreviously stated, the herein described invention is not to be limitedwith respect to any specific type of variable impedance employed forcontrolling the volume of sound. ln Figure 4 I show a conventional typeof potentiometer 15 which may take the form of any of the aforementionedtypes of devices of the prior art. For the sake of the invention, it is,therefore, immaterial as to whether the impedance is connected in acircuit controlled by variations in capacitance or by variations in aresistive element. It can be assumed that the potentiometer 15 includesa movable contactor, not shown, and that said contactor may movecounter-clockwise to a position where the potentiometer is in an offcondition or it may move clockwise to any degree and by even incrementsfor on conditions of the potentiometer and varying changes in theoverall volume of the produced sound. Similarly, the potentiometer maymove counter-clockwise for any desired gradual reduction in the overallvolume of sound. This contactor is fixed to a depending rotary shaft 16and fixed to the shaft is a sleeve 17, the latter having a laterallyextending knee-operated lever 17 as shown to advantage at Figures 1 and2. The volume control device with its lever 17 occupies a position in avertical plane to the right of the customary pedals 14' of the piano sothat when playing the instrument, the pedals can be operated whileoperating the lever 17 by the knee. lt is preferred that when the lever17' is in the position shown in Figure 1, the potentiometer will be in aneutral or off condition. To limit rotation of the shaft 16 in an offdirection, a stop 18 is employed and under the urge of a spring 19, theshaft is turned to engage said stop.

Referring now more particularly to Figure 2 wherein the invention isshown in detail, 20 designates a fiat metallic plate that can firmlyrest upon the floor. Pivoted to swing vertically on the plate is aclamping element 21. This may be inserted underneath the forward portionof the case of the piano at the bottom thereof, and by means of anadjusting screw 22 carried by the element 21, the screw may be advancedagainst the upper surface of the flat plate 21 to elevate the back endof the element and force integral spurs 23 of the element intoengagement with the case. Mounted for vertical tilting motion on thebase plate 20 is a foot-operated pedal 24. The mounting means embodies ahorizontally disposed rotary shaft 25 having at one end a gear pinion 26which meshes with a simiiar gear pinion 27 fixed to the lower end avertical shaft 23. The upper end of shaft 28 is secured in the reducedlower end 29 of a sleeve 3i), the latter being telescopically connectedwith the sleeve 17 and secured thereto to rotate therewith as shown at31. Interposed between the base plate 2% and the pedal 24 is a spring 32which tends normally to urge the pedal to an upwardly inclined orstarting position as shown in Figures land 2.

From the foregoing description of the constructional features of'theinvention, it follows that the shaft 23 may be vertically aligned withthe shaft 16 and the latter connected with the former so that both ofthese shafts will turn at the same time when lateral pressure is appliedthereto either by means of the gearing 26-27 or the knee-operated lever17. When the parts are thus connected, the knee-operated lever 17' maybe operated by the knee to adjust the potentiometer and hence theimpedance in the circuit of which it is a part or, and if desired,pressure of the foot may be applied to the pedal 24 to rotate the shaft28 in a clockwise direction and against the urge of either of theaforementioned springs. When pressure is gradually released from thepedal, the shaft 27 turns counter-clockwise, thus to restore thepotentiometer to a neutral condition.

What I claim as my invention is:

l. A foot control for an electrical volume control device of the classapplicable to the underside of the bedplank of a piano, which device isprovided with a depending volume control element mounted for rotationalmotion about a vertical axis; said foot control comprising a rigid base,expression pedal mounted on said base for tilting motion about ahorizontal axis, means for supporting said base against movement on thefloor and to dispose'same to one side of the foot pedals of the piano,and means for imparting rotational motion to said depending volumecontrol element in response to tilting motion of said expression pedal.

2. A foot control according to claim 1, wherein the motion impartingmeans comprises telescopically connected shafting including a topmostsleeve formed to receive said depending control element'and to befixedly secured thereto.

References Cited in the file of this patent UNITED STATES PATENTS1,893,895 Hammond, Jr. Jan. 10, .1933 2,221,274 Taylor Nov. 12, 19402,511,923 Larsen June 20, 1950 2,530,252 Luberofi Nov. 14, 19502,555,040 Jordan May 29, .1951

